中文摘要：

采用二次微波加热工艺制备硫酸镁水溶性砂芯,测试研究了增强剂高岭土对硫酸镁水溶性砂芯性能的影响,对比分析了二次微波加热制备的硫酸镁水溶性砂芯和二次微波硬化水玻璃砂的性能特征,通过扫描电子显微镜（SEM）分析了硫酸镁水溶性砂芯的微观形貌,采用优化配方的硫酸镁水溶性砂芯进行了AZ91D的浇铸试验.试验结果表明：二次微波加热制备的硫酸镁水溶性砂芯具有较高的抗拉强度、表面安定性和抗吸湿性,砂芯铸后的水溶溃散性良好,具有良好的应用前景.SEM分析结果表明：加入高岭土后水溶性砂芯粘结桥中的裂纹和孔隙减少,断裂方式由内聚断裂变成复合断裂.

英文摘要：

Twice microwave heating technology was applied to harden MgSO4 water soluble sand core, and the effect of kaolin reinforcement on properties of the core was tested.The performance characteristics of the MgSO4 water soluble sand core were also analyzed and compared with sodium silicate sand hardened by twice microwave heating technology.Scanning electron microscope（SEM）was used to investigate the micro-morphology of the MgSO4 water soluble sand core,and the optimized water soluble sand core was applied to cast AZ91Dalloy.The results indicate that the MgSO4 water soluble sand core hardened by twice microwave heating technology has advantages of high tensile strength, excellent surface stability,good humidity resistance,and high removability by collapsing in the water,which has good application prospects.The SEM analysis demonstrates that with the addition of kaolin,there are less cracks and holes in the binder bridge of the water soluble sand core,and the mixed-mode fracture mechanism is instead of the cohesive fracture mechanism.